1. Field of the Invention
This invention relates to a processing apparatus for automatically conducting a biochemical reaction processing. More particularly, the present invention relates to a sample processing apparatus and a sample processing method to be used in gene examinations for detecting a nucleic acid extracted from a sample.
2. Description of the Related Art
Gene analyses using a test piece such as a DNA microarray or a DNA chip have been and being popularly conducted in recent years. A DNA microarray is a type of detection device prepared by arranging DNA probes of a number of different kinds on and anchoring them to the surface of a substrate, which may be a piece of slide glass or a silicon substrate, as so many probe spots to form a matrix. Then, the DNA microarray and an analyte that is labeled typically with a fluorescent dye are brought into contact with each other under hybridizing conditions. The labeling substance is fixed onto the DNA microarray by way of a probe nucleic acid when the DNA microarray and the analyte contain nucleic acids that give rise to a hybridization reaction. Then, the type of the nucleic acids can be identified that gave rise to the hybridization reaction by detecting the position of the labeling substance on the DNA microarray where the hybridization reaction took place.
A typical processing flow of gene analysis shows a sequence of (1) extraction of a nucleic acid from a sample, (2) amplification of the extracted nucleic acid, (3) hybridization reaction of the amplified nucleic acid and a DNA microarray and (4) detection of the hybridization reaction. Of the above steps, the steps (1) through (3) require cumbersome operations of liquid handling and container handling for the sample and the reagent and hence there is a strong demand for automation from the viewpoint of saving both labor and time.
Several proposals have hitherto been made in attempts to realize automated biochemical reactions.
For example, Japanese Patent Application Laid-Open No. H05-307039 describes a technique of defining the processing time and the waiting time in each processing step as a function of the type of each sample. Then, priority is defined for each of the received samples in terms of the order of processing and the sample to be processed is selected according to the defined priority and the defined waiting time so that the detection process is started with the sample having the highest priority. The above-cited patent document discloses an antibody detection method of processing the sample having the highest priority among the samples that are ready for processing because of zero waiting time or the waiting time has already elapsed, during the waiting time of a preceding sample whose processing time has elapsed for the processing step. The above-cited method enables to effectively exploit the waiting time so as to process the sample with a different processing sequence or process some other samples or add a new sample on the way of the processing operation.
Japanese Patent Application Laid-Open No. 2003-098180 discloses a system for determining the timing of conveying a plurality of sample processing units that are linked to each other according to the idleness of the receiving place and the waiting place of each processing unit. The system can rationally distribute objects of conveyance in a simple manner and such a system can be configured with ease regardless of the number of linked sample processing units.
Apparatus equipped with processing units capable of processing a plurality of successive steps may typically involve labor saving and time saving arrangements for conducting biochemical reactions. Desirably, such apparatus can process a plurality of samples by means of a single processing unit to improve the processing efficiency.
Meanwhile, the timing of actually starting a reaction processing of each sample cannot be determined in a simple manner. A large number of samples may be brought in beyond the processing capacity of an apparatus or a small number of samples may be brought in so as to be processed sequentially with a small time lag. As many samples as the processing section can accommodate may be set for processing in the former occasion. In the latter occasion, however, the processing efficiency of the apparatus can fall to increase the total processing time of processing a large number of samples because the processing is conducted without utilizing the full processing capacity. Therefore, it is desirable that the processing section can process a plurality of samples independently at arbitrarily defined timings. In other words, it is necessary that the processing section is divided into a plurality of subunits that can operate independently.
When such an arrangement is employed, it is necessary to efficiently manage the schedule according to the sample processing situation in the apparatus in order to improve the processing efficiency of the apparatus. If the processing time of the steps is reduced in the future, more samples may need to be processed accordingly. In short, the importance of process scheduling will become much more important in the future.
From the viewpoint of samples, the results of examination can be affected by the time for which a sample is waiting for the processing. Therefore, if a sample and a reagent are held waiting in the apparatus, it is necessary to keep the sample and the reagent at low temperature or define the range of waiting time.
According to the above-cited Japanese Patent Application Laid-Open No. H05-307039, priority is defined for each of the samples received by the apparatus and the processing schedule is prepared for the plurality of samples. While this technique may be able to prevent the waiting time of a high priority sample from being prolonged, the waiting time of a low priority sample by conversely be prolonged. Additionally, when two or more than two samples are brought in with the same priority, it is not possible to prevent the waiting time from being prolonged.
According to the above-cited Japanese Patent Application Laid-Open No. 2003-098180, samples are brought to idle places by seeing the timing of conveyance, the waiting place and the receiving place for idleness. However, with this technique, the waiting time of a sample is long when there is not any idle place. The above-listed problems inevitably occur when samples are brought in without taking the processing capacity of the examination apparatus into consideration.